PROPOSAL (Adapted from the applicant's abstract): The rupture of intracranial aneurysms leads to hemorrhage in over 30,000 Americans annually, with mortality and morbidity exceeding 75%. Because these lesions can be repaired prophylactically, an understanding of the pathogenetic mechanisms and early identification would be of tremendous benefit. But the etiology of cerebral aneurysms remains unclear. The investigators propose to define the risk factors, incidence of familial aggregation, and patterns of inheritance in patients with cerebral aneurysms. They will pay particular attention to the ethnic background, and establish a blood and tissue bank for molecular analyses. They plan to utilize the large number of patients currently treated at the UTH, to identify 500 patients with cerebral aneurysms and 50 affected families that can be studied in a detailed and consistent manner. A strength of their patient population is the ethnic diversity of those treated: 41% Caucasian, 24% African-American, 26% Hispanic, and 9% Asian. Their hypothesis is that different ethnic groups will have different risk factors, patterns of familial aggregration, and inheritance of cerebral aneurysms. The following are their specific aims: 1) to compare the incidence of familial aneurysms in patients of different ethnic backgrounds and to establish the patterns of inheritance; 2) to compare the risk factors for cerebral aneurysm in patients with different ethnic backgrounds; and 3) to establish a blood and tissue sample bank for linkage and molecular analyses.